head to head
Neither is simply harder - they are hard in different places. Puyo Puyo! 15th Anniversary demands more optimization; Tetris 99 demands more execution.

Execution · Practiced Mastery
A competitive falling-blob puzzler about chaining combos faster than your opponent.

Execution · Pure Mechanics
Battle royale Tetris where raw stacking speed decides who outlasts 98 opponents.
Puyo Puyo! 15th Anniversary leans Execution (Practiced Mastery); Tetris 99 leans Execution (Pure Mechanics).
Tetris 99 leans clearly harder on execution.
Puyo Puyo! 15th Anniversary
Fast blob placement under pressure demands quick hands
Tetris 99
High-speed stacking and finesse define survival
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Puyo Puyo! 15th Anniversary
Versus play rewards reading opponent chain timing and counters
Tetris 99
Targeting and badge timing against humans matter mid-match
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Puyo Puyo! 15th Anniversary
Next-piece queue is random but bounded and visible
Tetris 99
Incoming garbage timing and piece sequence add chaos
Puyo Puyo! 15th Anniversary leans clearly harder on optimization.
Puyo Puyo! 15th Anniversary
Building large chains is a learnable scoring system
Tetris 99
Stacking theory and downstack efficiency are studied skills
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.